Messages in this thread | | | Subject | Re: [PATCH v3 06/11] iio: inkern: add module put/get on iio dev module when requesting channels | From | Eugen Hristev <> | Date | Tue, 17 Apr 2018 10:39:24 +0300 |
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On 17.04.2018 02:58, Dmitry Torokhov wrote: > On Sun, Apr 15, 2018 at 08:33:21PM +0100, Jonathan Cameron wrote: >> On Tue, 10 Apr 2018 11:57:52 +0300 >> Eugen Hristev <eugen.hristev@microchip.com> wrote: >> >>> When requesting channels for a particular consumer device, >>> besides requesting the device (incrementing the reference counter), also >>> do it for the driver module of the iio dev. This will avoid the situation >>> where the producer IIO device can be removed and the consumer is still >>> present in the kernel. >>> >>> Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com> >>> --- >>> drivers/iio/inkern.c | 8 +++++++- >>> 1 file changed, 7 insertions(+), 1 deletion(-) >>> >>> diff --git a/drivers/iio/inkern.c b/drivers/iio/inkern.c >>> index ec98790..68d9b87 100644 >>> --- a/drivers/iio/inkern.c >>> +++ b/drivers/iio/inkern.c >>> @@ -11,6 +11,7 @@ >>> #include <linux/slab.h> >>> #include <linux/mutex.h> >>> #include <linux/of.h> >>> +#include <linux/module.h> >>> >>> #include <linux/iio/iio.h> >>> #include "iio_core.h" >>> @@ -152,6 +153,7 @@ static int __of_iio_channel_get(struct iio_channel *channel, >>> if (index < 0) >>> goto err_put; >>> channel->channel = &indio_dev->channels[index]; >>> + try_module_get(channel->indio_dev->driver_module); >> >> And if it fails? (the module we are trying to get is going away...) >> >> We should try and handle it I think. Be it by just erroring out of here. > > Even more, this has nothing to do with modules. A device can go away for > any number of reasons (we unbind it manually via sysfs, we pull the USB > plug from the host in case it is USB-connected device, we unload I2C > adapter for the bus device resides on, we kick underlying PCI device) > and we should be able to handle this in some fashion. Handling errors > from reads and ignoring garbage is one of methods. > > FWIW this is a NACK from me. > > Thanks. Hello,
This patch is actually a "best effort attempt" for the consumer driver (touch driver) to get a reference to the producer of the data (the IIO device), when it requests the specific channels. As of this moment, there is no attempt whatsoever for the consumer to have a reference on the producer driver. Thus, the producer can be removed at any time, and the consumer will fail ungraciously. I can change the perspective from "best effort" to "mandatory" to get a reference to the producer, or you wish to stop trying to get any reference at all (remove this patch completely) ?
Thanks, Eugen
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